//! HTTP API模块
//! 
//! 提供RESTful HTTP接口

use crate::{Error, Result};
use std::sync::Arc;
use parking_lot::RwLock;

/// HTTP服务器（简化实现）
#[derive(Debug)]
pub struct HttpServer {
    /// 监听地址
    bind_address: String,
    /// 监听端口
    port: u16,
    /// 服务器统计信息
    stats: Arc<RwLock<HttpServerStats>>,
}

/// HTTP服务器统计信息
#[derive(Debug, Clone, Default)]
pub struct HttpServerStats {
    /// 总请求数
    pub total_requests: u64,
    /// 成功请求数
    pub successful_requests: u64,
    /// 失败请求数
    pub failed_requests: u64,
    /// 平均响应时间（毫秒）
    pub avg_response_time_ms: u64,
    /// 活跃连接数
    pub active_connections: u64,
}

/// HTTP请求类型
#[derive(Debug, Clone)]
pub enum HttpRequest {
    /// 查询请求
    Query { sql: String },
    /// 健康检查
    HealthCheck,
    /// 获取统计信息
    Stats,
    /// 获取表列表
    ListTables,
    /// 获取表结构
    DescribeTable { table_name: String },
}

/// HTTP响应
#[derive(Debug, Clone)]
pub struct HttpResponse {
    /// 状态码
    pub status_code: u16,
    /// 响应体
    pub body: String,
    /// 响应头
    pub headers: std::collections::HashMap<String, String>,
}

impl HttpServer {
    /// 创建新的HTTP服务器
    pub fn new(bind_address: String, port: u16) -> Self {
        Self {
            bind_address,
            port,
            stats: Arc::new(RwLock::new(HttpServerStats::default())),
        }
    }

    /// 获取服务器统计信息
    pub fn get_stats(&self) -> HttpServerStats {
        self.stats.read().clone()
    }

    /// 重置统计信息
    pub fn reset_stats(&self) {
        let mut stats = self.stats.write();
        *stats = HttpServerStats::default();
    }
    
    /// 启动服务器
    pub async fn start(&self) -> Result<()> {
        tracing::info!("启动HTTP服务器 {}:{}", self.bind_address, self.port);

        // 简化实现，实际需要使用axum或其他HTTP框架
        // 这里模拟服务器启动
        self.increment_active_connections();

        Ok(())
    }

    /// 处理HTTP请求
    pub async fn handle_request(&self, request: HttpRequest) -> Result<HttpResponse> {
        let start_time = std::time::Instant::now();

        // 更新统计信息
        {
            let mut stats = self.stats.write();
            stats.total_requests += 1;
        }

        let response = match request {
            HttpRequest::Query { sql } => {
                self.handle_query(sql).await
            }
            HttpRequest::HealthCheck => {
                self.handle_health_check().await
            }
            HttpRequest::Stats => {
                self.handle_stats_request().await
            }
            HttpRequest::ListTables => {
                self.handle_list_tables().await
            }
            HttpRequest::DescribeTable { table_name } => {
                self.handle_describe_table(table_name).await
            }
        };

        // 更新响应时间统计
        let duration = start_time.elapsed().as_millis() as u64;
        {
            let mut stats = self.stats.write();
            if response.is_ok() {
                stats.successful_requests += 1;
            } else {
                stats.failed_requests += 1;
            }
            stats.avg_response_time_ms =
                (stats.avg_response_time_ms + duration) / 2;
        }

        response
    }

    /// 处理SQL查询请求
    async fn handle_query(&self, sql: String) -> Result<HttpResponse> {
        tracing::debug!("处理SQL查询: {}", sql);

        // 简化实现：返回模拟结果
        let mut headers = std::collections::HashMap::new();
        headers.insert("Content-Type".to_string(), "application/json".to_string());

        let body = serde_json::json!({
            "status": "success",
            "query": sql,
            "rows": [],
            "execution_time_ms": 10
        }).to_string();

        Ok(HttpResponse {
            status_code: 200,
            body,
            headers,
        })
    }

    /// 处理健康检查请求
    async fn handle_health_check(&self) -> Result<HttpResponse> {
        let mut headers = std::collections::HashMap::new();
        headers.insert("Content-Type".to_string(), "application/json".to_string());

        let body = serde_json::json!({
            "status": "healthy",
            "timestamp": chrono::Utc::now().to_rfc3339(),
            "version": env!("CARGO_PKG_VERSION")
        }).to_string();

        Ok(HttpResponse {
            status_code: 200,
            body,
            headers,
        })
    }

    /// 处理统计信息请求
    async fn handle_stats_request(&self) -> Result<HttpResponse> {
        let stats = self.get_stats();
        let mut headers = std::collections::HashMap::new();
        headers.insert("Content-Type".to_string(), "application/json".to_string());

        let body = serde_json::json!({
            "total_requests": stats.total_requests,
            "successful_requests": stats.successful_requests,
            "failed_requests": stats.failed_requests,
            "avg_response_time_ms": stats.avg_response_time_ms,
            "active_connections": stats.active_connections
        }).to_string();

        Ok(HttpResponse {
            status_code: 200,
            body,
            headers,
        })
    }

    /// 处理表列表请求
    async fn handle_list_tables(&self) -> Result<HttpResponse> {
        let mut headers = std::collections::HashMap::new();
        headers.insert("Content-Type".to_string(), "application/json".to_string());

        // 简化实现：返回模拟表列表
        let body = serde_json::json!({
            "tables": ["users", "orders", "products"]
        }).to_string();

        Ok(HttpResponse {
            status_code: 200,
            body,
            headers,
        })
    }

    /// 处理表结构描述请求
    async fn handle_describe_table(&self, table_name: String) -> Result<HttpResponse> {
        let mut headers = std::collections::HashMap::new();
        headers.insert("Content-Type".to_string(), "application/json".to_string());

        // 简化实现：返回模拟表结构
        let body = serde_json::json!({
            "table_name": table_name,
            "columns": [
                {"name": "id", "type": "INTEGER", "nullable": false},
                {"name": "name", "type": "VARCHAR", "nullable": true}
            ]
        }).to_string();

        Ok(HttpResponse {
            status_code: 200,
            body,
            headers,
        })
    }

    /// 增加活跃连接数
    fn increment_active_connections(&self) {
        let mut stats = self.stats.write();
        stats.active_connections += 1;
    }

    /// 减少活跃连接数
    fn decrement_active_connections(&self) {
        let mut stats = self.stats.write();
        if stats.active_connections > 0 {
            stats.active_connections -= 1;
        }
    }
    
    /// 停止服务器
    pub async fn stop(&self) -> Result<()> {
        tracing::info!("停止HTTP服务器");
        Ok(())
    }
}

/// HTTP API路由
#[derive(Debug)]
pub struct ApiRoutes;

impl ApiRoutes {
    /// 创建路由
    pub fn create_routes() -> Self {
        Self
    }
    
    /// 健康检查端点
    pub async fn health_check() -> Result<String> {
        Ok("OK".to_string())
    }
    
    /// 执行SQL查询端点
    pub async fn execute_query(_query: String) -> Result<String> {
        // 简化实现
        Ok("Query executed".to_string())
    }
    
    /// 获取数据库状态端点
    pub async fn database_status() -> Result<String> {
        Ok("Database is running".to_string())
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    
    #[test]
    fn test_http_server_creation() {
        let server = HttpServer::new("127.0.0.1".to_string(), 8080);
        assert_eq!(server.bind_address, "127.0.0.1");
        assert_eq!(server.port, 8080);
    }
    
    #[tokio::test]
    async fn test_health_check() {
        let result = ApiRoutes::health_check().await.unwrap();
        assert_eq!(result, "OK");
    }
    
    #[tokio::test]
    async fn test_execute_query() {
        let result = ApiRoutes::execute_query("SELECT 1".to_string()).await.unwrap();
        assert_eq!(result, "Query executed");
    }

    #[tokio::test]
    async fn test_http_request_handling() {
        let server = HttpServer::new("127.0.0.1".to_string(), 8080);

        // 测试健康检查请求
        let health_request = HttpRequest::HealthCheck;
        let response = server.handle_request(health_request).await.unwrap();
        assert_eq!(response.status_code, 200);
        assert!(response.body.contains("healthy"));

        // 测试SQL查询请求
        let query_request = HttpRequest::Query {
            sql: "SELECT * FROM users".to_string(),
        };
        let response = server.handle_request(query_request).await.unwrap();
        assert_eq!(response.status_code, 200);
        assert!(response.body.contains("success"));
    }

    #[tokio::test]
    async fn test_stats_tracking() {
        let server = HttpServer::new("127.0.0.1".to_string(), 8080);

        // 初始统计信息
        let stats = server.get_stats();
        assert_eq!(stats.total_requests, 0);
        assert_eq!(stats.successful_requests, 0);

        // 处理一些请求
        let request1 = HttpRequest::HealthCheck;
        server.handle_request(request1).await.unwrap();

        let request2 = HttpRequest::Stats;
        server.handle_request(request2).await.unwrap();

        // 检查统计信息
        let stats = server.get_stats();
        assert_eq!(stats.total_requests, 2);
        assert_eq!(stats.successful_requests, 2);
        assert_eq!(stats.failed_requests, 0);

        // 重置统计信息
        server.reset_stats();
        let stats = server.get_stats();
        assert_eq!(stats.total_requests, 0);
    }

    #[tokio::test]
    async fn test_table_operations() {
        let server = HttpServer::new("127.0.0.1".to_string(), 8080);

        // 测试表列表请求
        let list_request = HttpRequest::ListTables;
        let response = server.handle_request(list_request).await.unwrap();
        assert_eq!(response.status_code, 200);
        assert!(response.body.contains("tables"));

        // 测试表结构描述请求
        let describe_request = HttpRequest::DescribeTable {
            table_name: "users".to_string(),
        };
        let response = server.handle_request(describe_request).await.unwrap();
        assert_eq!(response.status_code, 200);
        assert!(response.body.contains("users"));
        assert!(response.body.contains("columns"));
    }

    #[test]
    fn test_http_server_stats() {
        let server = HttpServer::new("127.0.0.1".to_string(), 8080);

        // 测试连接计数
        server.increment_active_connections();
        server.increment_active_connections();
        let stats = server.get_stats();
        assert_eq!(stats.active_connections, 2);

        server.decrement_active_connections();
        let stats = server.get_stats();
        assert_eq!(stats.active_connections, 1);
    }
}
